Unregulated Wattage

[Carl Fredrik Ahl]

Hi,

I wonder how devices like vapes for example can have the same wattage until the battery dies. Shouldn't wattage drop down when the battery level drops, because then the voltage will be lower?

[StringJunky]

I think the voltage regulator in a regulated device swaps voltage for current as the voltage drops to maintain the watts.  When it drops to about 3.2v the device will shut down to protect the battery. The load on the battery increases to maintain the power. 

Edited March 14, 2019 by StringJunky

[Carl Fredrik Ahl]

3 hours ago, StringJunky said:

I think the voltage regulator in a regulated device swaps voltage for current as the voltage drops to maintain the watts.  When it drops to about 3.2v the device will shut down to protect the battery. The load on the battery increases to maintain the power. 

My device's output voltage is from 0.5 to 9 volts and the battery is 1600mAh. If it uses 9 volt when vaping 50 watts, how can it then vape at 50 watts when the voltage drops down to like 5 volts for example? Thx for the answer, but can you explain in more detail plz?

[StringJunky]

6 minutes ago, Carl Fredrik Ahl said:

My device's output voltage is from 0.5 to 9 volts and the battery is 1600mAh. If it uses 9 volt when vaping 50 watts, how can it then vape at 50 watts when the voltage drops down to like 5 volts for example? Thx for the answer, but can you explain in more detail plz?

Try this: https://www.reddit.com/r/electronic_cigarette/comments/3kogxd/psa_you_dont_calculate_current_draw_on_regulated/

 

[studiot]

11 minutes ago, Carl Fredrik Ahl said:

My device's output voltage is from 0.5 to 9 volts and the battery is 1600mAh. If it uses 9 volt when vaping 50 watts, how can it then vape at 50 watts when the voltage drops down to like 5 volts for example? Thx for the answer, but can you explain in more detail plz?

The wattage changes, although you have some control by also changing the resistance.

See here for a detailed chart and explanation.

https://www.ecigarettedirect.co.uk/ashtray-blog/2014/04/electronic-cigarette-batteries-guide.html

[StringJunky]

10 minutes ago, studiot said:

The wattage changes, although you have some control by also changing the resistance.

See here for a detailed chart and explanation.

https://www.ecigarettedirect.co.uk/ashtray-blog/2014/04/electronic-cigarette-batteries-guide.html

A 'variable wattage' device means it is user variable, not device variable. The same with a 'variable voltage' device. The respective parameters are held constant until the battery can't cope.

Edited March 14, 2019 by StringJunky

[Carl Fredrik Ahl]

1 hour ago, StringJunky said:

Try this: https://www.reddit.com/r/electronic_cigarette/comments/3kogxd/psa_you_dont_calculate_current_draw_on_regulated/

 

Thx, now I understand, when the voltage of the battery drops, more current is needed instead so more amps will be used, but how can the circuit decide how many amps will be used? How can it increase the current when the voltage get lower?

[Janus]

1 hour ago, Carl Fredrik Ahl said:

Thx, now I understand, when the voltage of the battery drops, more current is needed instead so more amps will be used, but how can the circuit decide how many amps will be used? How can it increase the current when the voltage get lower?

A voltage regulator works by maintaining a set output voltage.  This set voltage will be less than the nominal voltage available from the source, such as a battery. So you might have a 5 volt regulator being sourced by a 9 volt battery.  

A typical voltage regulator uses a voltage reference such as a Zener diode.  A Zener diode has a specific break down voltage, which allows it to maintain a constant voltage drop regardless of the current flowing through it ( within limits).   The regulator then compares this to its output. If the current load on the regulator increases and tries to draw down the output voltage, the regulator compensates by drawing more current from the battery.   This of course draws down the voltage of the battery. This only becomes a problem if the battery voltage drops too close to the required regulated output voltage.    As long as the battery is rated with a voltage greater than the regulated voltage by enough leeway,  you would get a constant voltage output from the regulator for quite a while; right up to the point where the battery drops to the cutoff point.

To maintain a constant wattage, the output voltage of the regulator would change to compensate.    So for example, if you want to maintain a constant  1 mw of power, and the load is 25k ohm, the output voltage would be 5v, and a current draw of 0.2 ma.     If the load changed to a resistance of 10 k ohm,  the output voltage would need to drop to ~3.16 v as the current raises to ~3.16 ma. 

On the other hand, if these two resistors were connected directly to a 5v battery, you would still get the 1 mw power on the 25 k load, but with the 10k load, the power would jump to almost 2.5 mw.

The regulator controls the output and draws on the battery to do so.  The battery just needs needs to be large enough to meet these needs even after it's no longer operating at its fully rated voltage.

[studiot]

 

 

27 minutes ago, Janus said:

A voltage regulator works by maintaining a set output voltage.  This set voltage will be less than the nominal voltage available from the source, such as a battery. So you might have a 5 volt regulator being sourced by a 9 volt battery. 

 

4 hours ago, StringJunky said:

A 'variable wattage' device means it is user variable, not device variable. The same with a 'variable voltage' device. The respective parameters are held constant until the battery can't cope.

I think there are some misunderstandings here.

Firstly there are several electronic ways to control power and voltage.
Yes, stringjunky the user has a variable setting knob or dial. But this merely activates the control mechanism/circuitry within the device.

 

It should be remembered that the vapours are generated by applying electrical power to a resistive heating element (called the coil by mnufacturers).
The characteristics of both this coil and the liquid feed combine to determine the heating effect and vapour generation.

I do not know whether vape devices in general or the OP's particular device inparticular are pulse or plain DC driven.
It is likely that the thermal inertia would be too great for tight control at DC, so I would expect some form of electronic pulses to be used.

The tables in the article I linked to suggest that only simple DC power is employed and that users substitute batteries and coils rather too freely.

 

[StringJunky]

22 minutes ago, studiot said:

 

 

 

I think there are some misunderstandings here.

Firstly there are several electronic ways to control power and voltage.
Yes, stringjunky the user has a variable setting knob or dial. But this merely activates the control mechanism/circuitry within the device.

 

It should be remembered that the vapours are generated by applying electrical power to a resistive heating element (called the coil by mnufacturers).
The characteristics of both this coil and the liquid feed combine to determine the heating effect and vapour generation.

I do not know whether vape devices in general or the OP's particular device inparticular are pulse or plain DC driven.
It is likely that the thermal inertia would be too great for tight control at DC, so I would expect some form of electronic pulses to be used.

The tables in the article I linked to suggest that only simple DC power is employed and that users substitute batteries and coils rather too freely.

 

How do you mean?

[studiot]

9 minutes ago, StringJunky said:

and that users substitute batteries and coils rather too freely.

If you mean this bit, I'm sorry if I implied that the tables suggest this.

There were safety paragraphs and a video/ animation in the article about not doing mix and match, which implies to me that folks do more than paint puff harder stripes on the sides of their device.

 

[StringJunky]

12 minutes ago, studiot said:

If you mean this bit, I'm sorry if I implied that the tables suggest this.

There were safety paragraphs and a video/ animation in the article about not doing mix and match, which implies to me that folks do more than paint puff harder stripes on the sides of their device.

 

Yeah, some people have no idea and are literally playing with fire by combining components that can't cope with the loads.